Avitus
The avitus locus first became noticed in the stallion Aviter, for which it is named, who was born to a survivor of the plague that ravaged the island of Vicus many years before. It controls whether patchy pale markings are seen on the horse's coat, and whether those pale markings represent simply a reduction in colour of the underlying base coat, or a complete loss of it, leading to the markings being white. It's alleles are heavily associated with different islands and are associated with build. When creating a custom horse (or using the custom previewer), the user is asked to select the specific genotype at the avitus locus, rather than choosing a phenotype and having the game select an appropriate genotype. Alleles There are two avitus alleles, with no particular dominance hierarchy. av The av allele represents the inactive form of the gene, and confers no pattern upon the horse's coat. It is co-dominant with respect to the less common AV allele, and is found on all Paradisus islands. It is unaffected by build phenotype and can be obtained using a Drop Gene item and selecting 'Avitus'. When the avitus locus is homozygous for av, it is not displayed in the genetics section of horse's character page. AV The AV allele represents the active form of the gene, conferring a colour-reducing affect in patches across a horse's coat. It is co-dominant with respect to but much rarer than av, and is only found on Vicus. It is this allele that first cropped up in the stallion Aviter, av having only existed previously. It is not limited by build phenotype and can be obtained using an Add A Gene: Avitus item. It is inactive on donkeys and mules. Phenotypes Non-Avitus (avav) The non-avitus phenotype simply lacks any avitus-related reduction in colour of the coat, resulting in a solid, unpatchy appearance unless other white marking alleles from other loci are present. Merle Avitus (AVav) Usually referred to as simply avitus, the merle avitus phenotype is the result of a single AV allele working alone. It results in patches on the horse's coat where the underlying colour is reduced, making it paler than the surrounding coat, though it is not fully reduced to white. The patches are usually quite jagged and varying in their degree of paling to give a mottled appearance on affected areas. They are usually fairly evenly distributed across the horse's body, legs and head. The colour of the mane and tail of a merle avitus horse is also reduced. This phenotype is never seen on donkeys or mules, even if their genetics supports it. Harlequin Avitus (AVAV) Also usually referred to as just avitus, with no distinction made between the merle and harlequin states, harlequin avitus is the effect of two AV alleles exerting their effect. In this state, the pale patches of a merle avitus horse are thoroughly drained of colour, making them fully white in places, thoguh some mottling is still evident in some cases. The patches are shaped and distributed in a similar manner to those of a merle avitus horse. This phenotype is never seen on donkeys or mules, even if their genetics supports it. Category:Marking Genetics